Boris Johnson quits in protest over May's Brexit plan

Both Mr Johnson and Mr Davis had signed up on Friday to Mrs May's blueprint for Brexit at an all-day summit at Chequers which the Prime Minister believed had secured Cabinet unity behind her proposals.

He told the Prime Minister: 'As I said then, the Government now has a song to sing.

"The government now has a song to sing. The trouble is that I have practised the words over the weekend and find they stick in the throat", he wrote.

With less than nine months left before Britain is due to leave the EU, and just over three before the EU says it wants a deal, European Council President Donald Tusk raised the idea that Brexit might be called off.

May had been reluctant to spell out her strategy until now precisely for fear of igniting furious rows in her deeply divided Conservative Party.

"My concern is about the policy rather than the individual", he said.

The GBP/USD is hesitating near the 1.3300 major level As Monday's Brexit revelations roil Sterling traders and force the GBP back down as the chasm between Prime Minister Theresa May and hard-line Brexiteers within the parliament continues to widen.

Mr Davis said "the general direction of policy will leave us in at best a weak negotiating position, and possibly an inescapable one".

Davis also said that May's plan "would be a risk at least of delivering a poor outcome". He said it involved too close a relationship with the European Union and gave only an illusion of control being returned to the United Kingdom after it left the bloc.

Government unity began to fray within hours.

Other Brexit-supporting Conservative lawmakers have criticised the Chequers "peace deal", saying that May's plans offered a Brexit in name only, a betrayal of what they saw as her promise for a clean break with the EU.

One of the leading campaigners for leaving the European Union, the radio show personality and European parliamentarian Nigel Farage, said: "For Brexit to succeed we must get rid of this bad, duplicitous PM". Meanwhile, President Donald Trump is scheduled to arrive Thursday for a visit that will be closely watched for any comments on Brexit and US relations with the EU.

May has hung on to power longer than many expected after she lost her majority in a June 2017 snap election that she had called in hopes of strengthening her hand in Brexit talks.

But May's allies fear more resignations may follow. May replaced him with another Brexit campaigner, junior minister Dominic Raab.